This invention relates generally to compatibilizing agents and, more specifically, to compatibilizing agents for use in producing polymer blends.
Polymer blends are commonly used to combine in a single material a compromise of properties of two different polymers. Unfortunately, due to thermodynamic incompatibility it is often difficult to obtain a blend morphology conducive to useful mechanical properties, e.g., an optimally dispersed phase size and adequate interphase adhesion As a result, considerable research has been directed at development of compatibilizers, i.e., interfacial agents that lower the interfacial tension between the phases of an immiscible polymer blend. Compatibilizers yield smaller dispersed phase sizes and improved mechanical properties. The most common compatibilizers are block copolymers and ionomers, specifically poly(ethylene-co-methacrylic acid) and poly(ethylene-co-acrylic acid) ionomers.
Nylon-6 (N6) is an example of a commercially important engineering thermoplastic. A weakness of N6 is its fracture toughness which has been alleviated in the past by the addition of rubber to N6 and is widely practiced as evidenced by the large number of patents concerned with the development of supertough nylons; see Sen. A., Weiss, R. A., Garton, A. in Multiphase Polymers: Blends and Ionomers, Utracki, L. A. Weiss R. A., Eds., ACS Symp. Set. No. 395, Amer. Chem. Soc., 1989, p. 353. A relatively recent paper by Oshinki, A. J.; Paul, D. R.; Keskkula, H., Polymer Communications, 1991, 32, 12, 370 describes the use of hydrogenated styrene-butadiene-styrene block copolymers (SEBS) and maleated SEBS (M-SEBS) for toughening N6. The M-SEBS was used as a compatibilizing agent to reduce the dispersed rubber phase size, which resulted in significant toughening of the N6.
However, several problems arise in the use of maleated block copolymers. For example, there is a relatively high cost associated with producing block copolymers. Moreover, hydrogen bonding between the N6 and the carboxylate may also be relatively weak due to the relative weakness of maleic acid.